This invention relates to an exhaust gas purifying device for marine engines and more particularly to a device that will insure exhaust gas purification under all running conditions.
Although exhaust emission control has been practiced for a fairly substantial period of time in connection with motor vehicles such as automobiles and motorcycles, it has only been recently that there has been an interest in purifying the exhaust gases of marine engines such as outboard motors. In some ways, it is even more important to purify the exhaust gases of a marine engine since frequently the exhaust gases are discharged through the body of water in which the watercraft is operating back to the atmosphere. Therefore, in addition to the removal of certain atmospheric harmful constituents from the exhaust gases, it is desirable to insure that materials which might contaminate the body of water in which the watercraft is operating are also removed from the exhaust gases. In addition to removing different types of contaminates from the exhaust gases in marine applications from land applications, the running conditions of the marine engine are substantially different from those of automotive engines. Specifically, it is quite a common occurrence that a marine engine will be started and operated at low speeds for long periods of time. For example, it is quite common for a marine engine to be started and operated at trolling speeds for a long period of time. This gives rise to a considerable problem in connection with the use of catalytic exhaust treatments.
As is well known, a catalyst has a certain minimum operating temperature below which is not effective in achieving the desired gas treatment. Although the catalyst has a minimum operative temperature, it is also well known that once a catalyst reaches its operating temperature, the reaction of the exhaust gases tends to cause the catalyst to remain heated even though the exhaust gas temperature may be relatively low.
It is, therefore, a principle object of this invention to provide an improved exhaust gas purifying device for a marine engine.
It is a further object of this invention to provide an exhaust gas purifying device for a marine engine wherein a catalyst is employed wherein the catalyst will be heated even though the engine is started and operated in conditions when the catalyst would not be normally heated to its operating temperature.
It is a yet further object of this invention to provide an improved arrangement for bringing a catalytic exhaust gas purifier for a marine engine up to its operating temperature rapidly and regardless of the engine operating conditions.